You can try with some methods for solving trigonometric equations... For example putting ##X=\cos{\alpha}## and ##Y=\sin{\alpha}## you can form the system ##\left\{ \begin{array}{rl} -25FX+1.5FY=-80 \\ X^2+Y^2=1 \end{array} \right.##

You can try with some methods for solving trigonometric equations... For example putting ##X=\cos{\alpha}## and ##Y=\sin{\alpha}## you can form the system ##\left\{ \begin{array}{rl} -25FX+1.5FY=-80 \\ X^2+Y^2=1 \end{array} \right.##